2026 Gas Turbine Engines Practice Test – Full Prep for Components and Maintenance

The main idea is that the parts most exposed to wear from electrical contact in a starter-generator are the ones that actually transfer current and slide against each other. The brushes ride on the commutator to carry current into the rotor, and the commutator surface is what the brushes contact. Over time these surfaces wear, so periodic inspection is essential to catch wear before it causes trouble.

Brushes should be checked for length, wear, chipping, and proper seating in their holders, along with the spring tension that keeps them pressed against the commutator. If brushes are worn down or not seating correctly, contact becomes unreliable, increasing resistance, causing arcing, overheating, and potential loss of starting power. The commutator surface should be examined for scoring, grooves, glazing, discoloration, or any signs of overheating; such conditions indicate poor contact or accelerated wear and may require reface/reaming or replacement of the commutator, and sometimes replacement of worn brushes.

While other components like bearings, housing, or cooling fins may be inspected during maintenance, they do not require the same type of periodic inspection as the electrical-contact wear surfaces.